Comparison of United States Air Force PCI Standard Deviation Values to Default Values to Default Values in ASTM D5340
Pullen, Aaron B.
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This paper presents the results of an analysis of nearly 20 years of Pavement Condition Index (PCI) inspection data from the United States Air Force (USAF), comprised of over 10,000 inspected pavement sections, and compares the standard deviation of the PCI of individual sample units within pavement sections to the published defaults in ASTM D5340 (Standard Test Method for Airport Pavement Condition Index (PCI) Surveys), which is 10 points for asphalt pavements and 15 for Portland cement pavements. The USAF is committed to proactively maintaining and rehabilitating its airfields, in part through performing routine PCI surveys to identify and document distresses present in its airfield pavements. Pavements are divided into sections for inspection based on the pavement design, construction history, and traffic area. Because of the time and effort involved, surveys of entire sections are often beyond available manpower, funding, or time. A statistical sampling routine is defined in ASTM D5340 to reduce the effort required to determine the PCI of a given section of pavement. The sampling rate calculation is based on surveying enough samples to achieve a 95% confidence interval of + or - 5 PCI points and is calculated using the number of sample units and the standard deviation of PCI values of sample units in the section. The standard deviation is not known until after the survey has been accomplished; therefore, default values are provided. This study calculates the standard deviation for each inspected section and compares the results to the defaults. The paper also investigates the effect of other factors such as pavement use, pavement rank, age at time of inspection, and slab size on PCI standard deviation. Results indicate that the default values provided in the standard are generally not conservative for all pavements.